1. Field of the Invention
The present invention relates to a gasket for use in and in combination with a molding apparatus for casting articles out of plastics such as acrylic monomer or the like. More particularly, this invention relates to a new and improved gasket construction that is easier to use and further is imbued with a significantly greater operational life than those presently known in the prior art.
2. Description of the Prior Art
In the prior art processes for casting plastic articles out of acrylic monomer material or the like and more particularly for casting flat sheets, a monomer or a partial polymer of synthetic resin is introduced into a cavity defined by two generally horizontal parallel plates of glass, metal or other smooth inert material and gasket members disposed between the plates and adjacent the periphery thereof. In the known prior art molding apparatuses, the gaskets are compressed between the plates to allow for shrinkage of the polymerizing sheet without separation of the sheet from the mold surface. Compression of the gasket between the plates or molding surfaces is achieved by use of a press or clamping device during the polymerization and curing phase of the product to obtain a uniformly solid sheet.
The known prior art gaskets in use frequently, because of their composition, such as rubber, both natural and synthetic, suffer a breakdown during the casting operation whereupon certain particles migrate into the casting cavity and contaminate the sheet to be cast as well as to provide a sheet having voids or sink holes therein. Moreover, the prior art gaskets frequently adhere to the glass plates and/or the cast sheet so that separation therefrom is difficult. Prior art gaskets further frequently subject the operator of the molding apparatus to severe shock due to static electricity on separation of the glass plates defining the cavity from the molded sheet.